1. Field of the Invention
The present invention relates to an air passage opening and closing device for opening and closing an air passage and is effective as an air-mixing door for adjusting the ratio of an air flow of a hot air with respect to that of a cold air (air mixing ratio), a discharging mode switching door for switching the discharging mode, or the like, in an air conditioner for a vehicle.
2. Description of the Related Art
FIG. 1 is a drawing showing a structure of an indoor unit (the indoor unit is named so because it is arranged inside a vehicle compartment or near the compartment) of an air conditioner for a vehicle which has already been produced as a product and has been distributed on a market at the time of filing of the present application. FIG. 2 is an enlarged perspective view of A portion in FIG. 1 and FIG. 3 is a sectional view taken along the line 3A—3A in FIG. 2.
In FIG. 1, an air-conditioner casing 1 is a duct means which forms an air passage which is furnished in a vehicle compartment and from which air is discharged to an inside of the compartment. A blower (not shown) for supplying the air into the compartment is provided on a lower front side of the air-conditioner casing 1 in the drawing.
At the upstream side of an air flow in the air-conditioner casing 1, an evaporator 2 for cooling air discharged into the compartment is accommodated and all the air discharged from the blower passes through the evaporator 2.
At the downstream side of the air flow of the evaporator 2, a heater core 3 for heating air discharged into the compartment is accommodated and, at the same time, a bypass passage 4 to allow air, which has passed through the evaporator 2, to bypass the heater core 3 and to flow into the compartment side, is provided.
An air-mixing door 7 is an air flow ratio adjusting means for adjusting the air flow ratio of a cold air passing through the bypass passage 4 with respect to a hot air passing through the heater core 3. An air-mixing chamber 8 is an air-mixing chamber for mixing the cold air passing through the bypass passage 4 and the hot air passing through the heater core 3.
At the upper side of the air-mixing chamber 8, a face opening portion 9 communicating to a face discharge port (not shown) for discharging air to the upper side of the vehicle compartment through a duct (not shown) and a defroster opening portion 10 communicating to a defroster discharge port (not shown) for discharging air to vehicle windows (mainly to a front window glass) through a duct (not shown) are provided. On the other hand, at the lower side of the air-mixing chamber 8, a foot opening portion for discharging air to the lower side of the vehicle compartment.
A face door 11 is an opening and closing means for opening and closing the face opening portion 9, a defroster door 12 is an opening and closing means for opening and closing the defroster opening portion 10, and a foot door 13 is an opening and closing means for opening and closing the foot opening portion.
The air-mixing door 7, the face door 11, the defroster door 12 and the foot door 13 open and close the respective opening portions thereof by swinging (rotating) rectangular plate-like door bodies thereof, around the rotation axes of the opening portions as a center, by actuators such as a servo motor, etc. Because of the above configuration, the structure of opening and closing means will be explained below using an air-mixing door 7 as an example.
In FIG. 2, an opening portion 1a is an inlet port continuing to the evaporator 2 in air passages constituted by the air-conditioner casing 1 and the air-mixing door 7 is arranged at the upstream side of the air flow in the opening portion 1a so that it is possible to swing.
The air-mixing door 7 comprises: a substantially rectangular door body 7a for opening and closing the opening portion 1a; a shaft portion 7b acting as a swinging shaft of the air-mixing door 7, i.e. the door body 7a; an elastically deformable lip seal 7c which is arranged on a portion corresponding to the edge portions 1b of the opening portion 1a and in the edge side of the door body 7a and closes a gap created between the air-mixing door 7 and the edge portions 1b of the opening portion 1a when the opening portion 1a is closed by the air-mixing door 7; an elastically deformable second lip seal 7d which closes a gap at the shaft portion 7b side in the edge portions 1b of the opening portion 1a; and the like.
Particularly, the door body 7a and the shaft portion 7b are made of hard resin such as polypropylene and the lip seals 7c, 7d are made of flexible resin, such as elastomer, or rubber. Both of them are integrated by integral forming.
The sectional shape of the lip seal 7c is formed in a V shape, as shown in FIG. 3, so that a portion at which a side 7e shown at the upper side of the drawing (FIG. 3) and another side 7e shown at the lower side of the drawing are joined is positioned near to the door body 7a. The side 7e of the lip seal 7c at the lower side of the drawing is a seal means for closing gaps created between the air-mixing door 7 and the edge portions 1b of the opening portion 1a and the side 7e of the lip seal 7c at the upper side of the drawing is a seal means for closing gaps created between the air-mixing door 7 and edge portions 4a of the bypass passage 4 (refer to FIG. 1).
At the tips of the lip seal 7c, i.e. the tip sides of the sides 7e, protruding portions 7f protruding toward the edge portions 1b and toward the edge portions 4a are integrally formed with the lip seal 7c and, thereby, the sealing ability of the lip seal 7c is improved by contacting the tips of the protruding portions 7f to the edge portions 1b and 4a. 
Concretely, the protruding portion 7f totally forms a substantially C-shaped protruding line continuously provided on the totally substantially C-shaped lip seal 7c in a similar state to the lip seal 7c which is formed in a substantially C-shape on the end of the door body 7a. 
The second lip seal 7d is formed so that two sides 7e of the lip seal 7c forming a V shape are combined into one side and the other structure thereof is the same as that of the lip seal 7c. 
When the opening degree of the air-mixing door 7 is small, an uncomfortable noise such as “hyu”, “pyu” or “pyy” is likely to occur. The cause of the noise is generally as described below.
That is, when the opening degree of the air-mixing door 7 is small, as shown in FIG. 4, there may be a case in which air flows through a relatively small gap (a short distance) formed between the edge portion 1b of the opening portion 1a and the air-mixing door 7 in a laminar flow without being transformed into a turbulent flow. Part of an air flow after flowing through the air-mixing door 7 creates an exfoliating layer (an exfoliating flow) exfoliating from a main air flow, at the back side of the air-mixing door 7, and in a case in which the exfoliating layer grows into a row of vortexes, an uncomfortable noise such as “hyu” is created.
A means for reducing a noise caused by a row of vortexes created when air flows through a relatively small gap formed between an edge portion of an opening portion and an opening and closing door was conventionally realized by forming recesses and protrusions on the tip side of a lip seal to disturb an air flow passing through a gap between the lip seal and the edge portion of the opening portion and to prevent the air flow from being formed into a laminar flow, with a result preventing a row of vortexes from being created (for example, refer to Patent Document 1).
[Patent Document 1] Japanese Utility Model Publication No. 2,570,855
As the invention disclosed in Patent Document 1, however, relates to an opening and closing door for opening and closing a discharge port such as a face discharging port directly facing an inside of a vehicle compartment, it can not be applied to the air-mixing door 7 arranged in the air-conditioner casing 1, and the like, without modification and can not prevent efficiently the occurrence of a row of vortexes.